1. Field of the Invention
The invention relates to an information recording method for recording information to an information recording medium, an information recording apparatus, and an information recording medium. More particularly, the invention relates to the prevention of alteration of recording information on an information recording medium.
2. Related Background Art
Hitherto, various types of an information recording medium for magnetically or optically recording and reproducing information, such as disk-shape, card-shape, tape-shape, and the like, have been known. As such recording media, there are various kinds of media such as read only medium, recordable but unerasable medium, and recordable and erasable medium. Among those recording media, a card-shaped recording medium, particularly, a recording medium for optically recording and reproducing information by using a semiconductor laser (hereinafter, such a medium is referred to as an optical card) is small and light-weight, and is convenient for carrying, and has a relatively large storage or recording capacity. Therefore, a large demand is expected for recording medical information and personal information on this type of medium.
FIG. 1 is a plan view showing an example of such an optical card. FIG. 2 is a cross sectional view taken along the line 2--2 in FIG. 1. In the diagrams, reference numeral 5 denotes an optical card having a card shape. An information recording region 21 is provided on almost the whole surface of the optical card 5 and margin regions 22 are provided in partial regions in the upper and lower portions. A plurality of tracks 19 for tracking are preformatted in parallel at regular intervals in the information recording region 21 in order to perform an auto tracking. An information track 20 to record and reproduce information is provided between the tracks 19 for tracking. Track numbers 18 are used to discriminate each information track 20 and are preformatted at both ends of each information track 20.
As shown in FIG. 2, the optical card 5 is made up of a plurality of layers. A recording layer 24 is joined onto a substrate 26 by an adhesive agent layer 25. Further, a transparent protecting layer 23 is formed on the recording layer 24. The protecting layer 23 and recording layer 24 are formed so as to come into contact with each other by recess and projection shapes. With such a structure, the recording layer 24 is divided into the information tracks and the tracks for tracking. That is, a recess portion of the recording layer 24 corresponds to the information track 20 and a projection portion corresponds to the track 19 for tracking. As a recording layer 24, for example, a material such as silver salt system, dye system, chalcogen system, or the like is used.
To record information to such an optical card 5, a light beam of a semiconductor laser is converged to a micro light spot, the light spot is modulated in accordance with recording information to be recorded, and the modulated light spot is scanned onto the information track, so that the information is recorded onto the optical card 5 as an information pit train which can be optically detected. Since the information pit train is recorded by a physical change such as deformation, color change, or the like by light or heat, it is impossible to physically erase the information pit train which has once been recorded and to again use the region of the erased information pit train as a recording region. To reproduce the information pit train recorded on the optical card 5, a light beam of a predetermined intensity and of a certain degree such that recording cannot be performed is scanned on the information pit train. The reflected light (or transmitted light) from the optical card 5 at that time is detected by a photosensor, and a predetermined signal process such as binarization, demodulation, or the like is executed by using the derived detection signal, so that the recorded information is reproduced.
A file management for a system for recording and reproducing information by using an optical card will now be described. First, in a case of recording a certain amount of information onto the optical card, the information is recorded as a data file and information to manage the data file (hereinbelow, such information is referred to as a directory) is recorded in addition to the data file. Ordinarily, by separately recording the data file and the directory into the information recording region 21 in FIG. 1, file management can be easily performed. In a case of recording information, by recognizing recording start positions of the data file and the directory with reference to the directory of the relevant file, the data and the directory are recorded subsequent to the data and directory which were finally recorded, respectively.
At present, a method of using one optical card such as a medical card, bank card, or the like for a plurality of purposes by making the most of the characteristics such that the capacity is relatively large is considered as a using method of the optical card. That is, the optical card is used as a medical card to record personal medical data and the same optical card is used as a bank card in a bank or the like, thereby improving convenience. To use the optical card for multi purposes as mentioned above, therefore, as disclosed in, for example, JP-A-62-77959 (Laid-open No. 63-244385), there is known an information recording and reproducing method whereby a recording region of one optical card is divided into a plurality of blocks (partitions) and data and a directory are recorded to the respective partitions and each partition is used as one optical card.
In a case of using one optical card as a plurality of optical cards, from a viewpoint of protection of personal privacy, key information (hereinbelow, referred to as password information) to permit the recording and reproduction of information in every partition of the optical card is recorded so as to make it impossible to record and reproduce the information from an application (for example, application for a bank card) using one certain partition into a partition which is used by another application (for instance, application for a hospital card). There is used a method whereby in a case of recording and reproducing information to any one of the partitions, the password information corresponding to the partition is inputted, the inputted password information is collated with the password information recorded in the relevant partition, and only when both of the password information coincide, the recording and reproduction are permitted to the target partition.
The password information is recorded into a specific region of the partition. The apparatus or application manages the password information, thereby assuring security of the information of each partition. A method whereby information (for example, personal information or the like) which is commonly used for a plurality of applications is recorded in an area in a partition at one position and a plurality of applications access the partition by using the common password, thereby a method for efficiently using the memory capacity of the optical card is also known. Although the above description has been made with respect to the case where a plurality of applications use one optical card, even in a case where one application uses one optical card, there is also a case where the recording region of an optical card is similarly divided into a plurality of partitions.
Since the optical card as mentioned above is usually a WORM type recording medium, it is impossible to physically erase and rewrite the information once it has been recorded. Therefore, in such a WORM type recording medium, in a case of erasing recorded information, for example, as disclosed in JP-A-61-237033 (Laid-open No. 63-91888), there is used a method of logically erasing the information by recording information indicating that the information was erased to the information which has already been recorded. By using this method, after the information which had already been recorded was logically erased, by after-recording new information, an updating process of a file can be logically executed.
However, according to the method of logically updating the file by newly after-recording information to the recording medium, when contrarily considering, the important information on the recording medium can be simply altered by after-recording information. Therefore, to prevent such an information alteration, it is considered that a region to record specific important information or a partition is set to the minimum size that is necessary to record the specific important information.
However, if the size of partition is preset to the minimum size that is necessary to record information, when a recording error occurs, a problem would arise such that all of the information cannot be recorded because of the preset, minimum-sized recording region. As causes of the recording error, there are defects such as scratches or dust on the recording medium, and also causes which cannot be predicted such as a vibration which is applied from the outside upon recording or the like. It is, therefore, difficult to predict an amount of recording errors and to set the partition to the size that is necessary for recording information in consideration of the amount of recording errors. If the size of a partition is set to a sufficiently large size, there is a fear such that the information on the optical card is altered as mentioned above.
As mentioned above, hitherto, there is still room for alteration of the recorded important information by newly after-recording information into an unrecording region of the optical card. Particularly, such alteration is a fatal problem when the recorded information is information to confirm the user himself or information regarding a money process, for example.